There are a number of new microwave distribution systems under development using frequencies above 10000 MHz. Inter-satellite communications use the 28000 MHz frequency range. Multi-channel or interactive television would use the 27500-29500 MHz frequency range, while some wireless cable operators are opting for the 12 GHz CARS band. This activity has prompted a strong interest in base station antennas (similar to the broadcast television antennas). The antennas need to operate over a fairly wide bandwidth with a moderate to high power input. The azimuth coverage requirement, in most cases, is omnidirectional. The polarization may be either horizontal or vertical.
Omnidirectional antennas are traditionally arrays of basic radiating elements such as slots or dipoles. However the requirement for broad band operation is not compatible with linear array technology. The problem is further complicated by the relatively high power requirements (up to 2 Kw) at these high frequencies.